1. Field of The Invention
The present invention relates to a porous plate-shaped filler to form a heat insulation film in which a heat insulation effect improves, a heat insulation film including the porous plate-shaped filler, and a method for producing the porous plate-shaped filler.
2. Description of Related Art
As a heat insulation film formed on the surface of an article to improve a heat insulation effect and flame retardance of the article, there is known a film in which porous plate-shaped fillers having a low thermal conductivity are arranged in the form of layers in a matrix made of a resin or the like. Patent Document 1 discloses, as fillers to be included in a heat insulation film, porous plate-shaped fillers which are plates having an aspect ratio of 3 or more, a minimum length of 0.1 to 50 μm and a porosity of 20 to 99%. In the heat insulation film using the porous plate-shaped fillers, a length of a heat insulation route increases and a thermal conductivity can decrease as compared with a case of using spherical or cubic fillers. Consequently, even a thin heat insulation film has a heat insulation effect higher than before. Furthermore, a mutual bonding area of the porous plate-shaped fillers via the matrix is larger as compared with the case of using the spherical filler or the like, and hence strength can improve.
Furthermore, Patent Document 1 discloses, as a method for producing the porous plate-shaped filler, a method of firing a green sheet made of a material including ceramics powder and suitably grinding the fired green sheet. Furthermore, as another producing method, there is also disclosed a method of performing processing such as cutting or punching of the material in a state of the green sheet prior to the firing into a predetermined surface shape, and firing the green sheet to produce the porous plate-shaped filler without performing the grinding after the firing.